Myopia is a very common visual problem affecting millions of individuals in this country. It rarely requires thereapy other than spectacles or contact lenses. Radial keratotomy (RK) reduces corneal curvature and has now been performed in thousands of cases in the United States. Unfortunately, adequate studies of the safety and efficacy of this procedure have not been performed and complications such as endothelial cell loss, endophthalmitis, cataract, glare, and fluctuating vision have been reported. Our model of radial keratotomy in sub-human primates has been instrumental in altering the practice of radial keratotomy in regards number of incisions, depths of incisions, and length of incisions. The focus of the present renewal application is the corneal endothelium--the site of the most significant potential complication of radial keratotomy. Late bullous keratopathy, in fact, was a complication of a similar procedure performed in the late 1950's. Our goal is to determine the short and long term effects of radial keratotomy on the corneal endothelium in primates using wide field specular microscopy, corneal fluorophotometry, histopathology, and electron microscopy. Models of minimal, maximal, and moderate RK endothelial damage have been developed. We intend to determine the pathogenesis of endothelial cell damage in RK and to study the progressive endothelial cell loss in this model. We have also developed a stretch/flexion injury of the cornea to pursue the problem of continued corneal flexibility following RK. In addressing the important problem of the endothelial damage following RK, we will be answering important questions related to the safety of radial keratotomy. The relationship between corneal endothelial function and structure in our RK model system will allow correlation of early endothelial damage and early corneal endothelial dysfunction.